Incandescent electric lamp



INCANDES CENT ELECTR I C LAMP Filed June 20, 1938 Inventor; William-TCowhig, by HIM/75 His Att orney Patented Jan. 24, 1939 PATENT OFFICEINCANDESCENT ELECTRIC LAMP William '1. Cow l l;

General Electric New York Application June 20,

Bus y, Com

En land,

asslgnorto puma onol 1938, Serial No. 214,824

In Great Britain July 13, 1937 4 Claims.

The present invention relates to incandescent electric lamps and moreparticularly to such 'lamps in which a relatively short coiled filamentof a refractory metal such as tungsten is mounted within and sealed intoan envelope consisting of a tube of quartz or other like strong, heatresisting transparent or translucent vitreous material so as to lieaxially within the tube.

One of the dlfiiculties which arise when atungsten filament is mountedin a small quartz or glass envelope has been that the filament sagsduring operation and approaches the wall of the envelope. It is notconvenient to introduce a support along the length of the lamp owing tothe small diameter of the envelope, so that it is desirable to eliminatethis sag by drawing the iilarhent taut after it has been flash agedduring the lamp exhausting operation.

One object of my invention is to provide a method of mounting thefilament of an electric incandescent lamp so that it may be easily drawntaut without weakening the lamp envelope.

According to the invention, the sealing of the leading-in wiresinto thedrawn-down ends or neck portions of the tubular envelope is eflected atpoints somewhat spaced from the body of the envelope, and after theenvelope has been sealedoil the portion of one or both of the drawn-downends of the envelope, adjacent the body thereof,

is heated to soften it, and the leading-in wires,

Referring to the drawing, there is shown a typical double-ended lampcomprising a filament I mounted within a small tubular envelope 2preferably of quartz or other high heat-resistant glass. The filament Iis disposed substantially axially of the tubular envelope 2 which is ofrelatively small internal diameter. Opposite ends of the filament areconnected to current supply or leading-in wires sealed into reduced endor neck portions 2' of the lamp envelope 2, each of said wirescomprising a length of molybdenum wire 3 secured to the filament l, astrip of molybdenum foil attached to the wire 3, and a section ofmolybdenum strip 5 secured to the foil 4. The

;, actual seal between the quartz lamp envelope 2 and the current supplywires is made at the foil 4.

The filament assembly is sealed into the quartz or glass envelope 2 inthe usual way, using the above-described molybdenum strip seal. In the 5usual method of making these lamps, the seals are at a relatively shortdistance, such as 1 or 2 mm.', from the body of the lamp envelope 2.According to my invention, however, the seal is made at a considerablygreater distance from 10 the body of the lamp envelope, preferably at adistance of about to 1 cm. therefrom, as shown in the drawing. The lampenvelope is then exhausted through the exhaust tube Ii after which thefilament is then burned or flash aged in the .customary manner untilrecrystallization processes, etc., are complete. The exhaust tube 6having been tipped, the envelope neck portion A immediately adjacent thebody of the envelope 2 is then softened and the filament I drawn taut bya pulling-out or stretching operation. One or both of the envelope neckportions A between the body of the envelope and the current supply wireseal may be softened to permit this drawing-out Q or stretching of thefilament.

What I claim as new and desire to secure by Letters Patent of the United'States is:

1. The method of mounting a longitudinally extending coiled filament,having leading-in wires connected to its opposite ends, within a tubularglass envelope having reduced end portions, which comprises sealing saidleading-in wires into said reduced end portions, at least one of saidleading-in wires'being sealed at a point considerably removed from thebody of said envelope to thereby provide an extended neck portionbetween the body of, said envelope and the said seal, softening saidextended neck portion of said envelope, and then drawing the saidfilament' taut while the said extended neck por- 40 tion is stillplastic.

2. The method of mounting .a longitudinally extending coiled filament,having leading-in wires connected to its opposite ends, within a tubularglass envelope having 'reduced end portions, which comprises sealingsaid leading-in wires into said'reduced end portions'atpointsconsiderably removed from the body 'of said-envelope totherebyprovide extended neck per-- tions between the body of said envelope andthe said seals, softening at least one of said extended neck portions,-and then-drawing the said fila-' ment taut while the said extended neckportion is still plastic.

3. The method of mounting a longitudinally 56 extending coiled filament,having leading-in wires connected to its opposite ends, within a tubularglass'enveldpe having reduced end portions, which comprises sealing saidleading-in:

wires into said reduced end portions, at least one of said leading-inwires being sealed at a point considerably removed from the body of saidenvelope to thereby provide an extended neck portion between the body ofsaid envelope and the said seal, exhausting said envelope and operatingsaid filament until recrystallization thereof is-complete, softeningsaid extendedi-neck portion of said envelope, and then drawing the saidfilament taut while the said extended neck portion is still plastic.

4. The method of mounting a longitudinally extending coiled filament,having leading-in V wires connected to its opposite ends, within atubular glass envelope having reduced end por-.

ment taut while the said extended neck portion a is still plastic.

WILLIAM '1. COWHIG.

